There is some truth in your editorial comments. Tariff issues, State's Rights, cultural identity, etc., were all contributing factors to the Civil War. But for the South, the most important factors were the economic benefits from the continuation of slavery and the loss of political parity with the North, Northwest, and West.
The Compromise of 1850, the Kansas-Nebraska Act of 1854, and the Dred Scott decision of 1857, mollified the South enough to prevent the coming conflict for a decade. But by the Spring of 1860, extremist political forces in the South were bent upon dissolving the Union. Southern Democrats conspired to wreck the nominating convention held in Charleston that year, if the Northern Democrats did not accede to Southern demands for a "Slave Code." The Southern Democrats walked out and eventually nominated their own candidate, Breckinridge.
Those who favored secession felt that they represented the "Spirit of '76," that they embodied the revolutionary patriotism of their forefathers. When Democrat President James Buchanan heard of South Carolina's vote to secede, he gave an address which was widely published. In it, Buchanan "told his Southern friends that the Union was more than a 'mere voluntary association of states,' and that the founding fathers had not been 'guilty of the absurdity of providing for its own dissolution.' Secession was 'neither more nor less than revolution,' and though people did have a right to revolt, the election of a President by constitutional measures did not 'justify a revolution to destroy this very Constitution.'" (Note that Buchanan's views were not dissimilar from those of Robert E. Lee.)
If the Southern States had truly felt oppressed, as in the sense of the Declaration of Indpendence, they had individually and collectively several lawful ways to test the concept of secession. (As had been noted several times in this thread, although the Constitution details ways a State can join the Union, not withstanding the the concepts of the political theorists of the day, it is utterly silent on methods for leaving the Union.
Although several States and Regions had rattled the cages in previous years about leaving the Union, most of the protestations were designed to gain attention to their parochial issues. Much is made about the individual State's "sovereignty." Even before the onset of the Revolutionary War, there was a Continental Congress, which was the first attempt at a confederated, national government. The Second Continental Congress of 1776 created a national army, navy, and postal service. Thus the absolute sovereignty of the Colony-States was diminished in certain ways. By the end of the war and independence from Great Britain, the 13 States acted in unison to approve Articles of Confederation (1781). The Articles "... attempted to retain as much independence and sovereignty of the individual states as possible, while establishing a central government to carry out important national functions." For instance, diplomatic relationships were conducted by the "United States." Under the Articles, state sovereignty was not absolute, and in fact, less so then under the original Continental Congresses. The States gave a little bit away in unanimous concent with the other States. The Congresses under the Articles created methods for expanding the nation. The Northwest Ordinance of 1787, pre-constitutional law which is valid to this day, established procedures for incorporating new territories.
The Article II reserved sovereignty to the States, but national business could be conducted on a "supermajority" basis. Some liken the Articles to a "treaty" between equals. It also provided for "perpetual union." But it was clear this first attempt at "constitutional" government was weak and ineffective. When Congress authorized a convention to "correct defects" in the Articles, they instead got an entirely new document and type of government. The new plan changed the "operating agreement" (to use a business term) between the States. Sovereignty was no longer the sole perogative of the States, but rather "the people," and was to be expressed in a national republican democracy.
As a product of this reorganization, the individual States were given the option of going on their own and not joining the Union. Although three States joined "with reservations," the people of all the existing States ratified the Constitution and agreed to the concept of a Nation greater than the sum of the individual States.
What might a Southern State, circa 1860, have done to lawfully leave the Union, other than unilateral secession?
(1) Certainly, the State's legislature and executive could have authorized the Congressional delegation to ask the other States for its release. Could Congress simply have passed a law, like the Northwest Ordinance, with a signature by the President, cutting a State free from the Union?
(2) Failing that, Congress could have passed a law detailing how a State or States could leave the Union.
(3) A State's government could have made a declaration of independence and sued in Federal court to determine if their unwritten "right of secession" existed. In 1860, the US Supreme Court still tilted decidely to the South, and it is not impossible that the Court would have aloowed this.
(4) The representatives of a State or region could have proposed a Constitutional Amendment clarifying the process of secession or dissolution of the Nation.
(5) The same people could have called for another Constitutional convention to propose a secession amendment.
To my knowledge, none of these steps were taken. The South chose take a quasi-legal step: unilateral secession. Secession was rebellion. Secession was revolution. The American Civil War was in reality the War for Southern Independence.
Jefferson Davis himself argued, "Secession belongs to a different class of remedies. It is to be justified upon the basis that the States are sovereign. There was a time when none denied it. I hope the time may come again when a better comprehension of the theory of our government, and inalienable rights of the people of the States, will prevent anyone from denying that each State is sovereign, and thus may reclaim the grants which it has made an agent whomsoever." But as we have seen in the Texas vs. White (1869) decision, post-Civil War, the Supreme Court ruled that the "right of secession" does not exist, and under of Constitution, never did exist. This is settled case law. The Supreme Court are the arbiters of the meaning of the constitution. Anyone who, today, argues that a right to secede exists in the Constituion, is mentally masturbating.
Perhaps Grant summed it up best with his observations:
"In the case of the war between the States it would have been the exact truth if the South has said, "We do not want to live with you Northern people any longer; we know our institution of slavery is obnoxious to you, and, as you are growing numerically stronger than we, it may at some time in the future be endangered. So long as you permitted us to control the government and with the aid of a few friends in the North to enact laws constituting your section a guard against the escape of our property, we were willing to live with you. You have been submissive to our rule heretofore; but it looks now as if you did not intend to continue so, and we will remain in the Union no longer."
Instead of this, the seceding states cried lustily, "Let us alone; you have no constitutional power to interfere with us." Individuals might ignore the Constitution; but the Nation itself must not only obey it, but must enforce the strictest construction of that instrument; the construction put upon it by the Southerners themselves. The fact is the constitution did not apply to any such contingency as the one existing from 1861 to 1865. Its framers never dreamed of such a contingency occurring. If they had foreseen it, the probabilities are they would have sanctioned the right of a State or States to withdraw rather than that there should be war between brothers.